The present disclosure relates to power transmission components and lubrication systems. Axle assemblies in wheeled vehicle drivetrains are known to employ a differential apparatus to permit an outer drive wheel to rotate at a greater velocity than an inner drive wheel when operating a vehicle through a turn. Differential apparatuses often employ a pinion gear drivingly engaged with a ring gear, which in turn rotates a differential case having a number of planet gears or bevel gears coupled with a pair of axles. The differential apparatus is located within a carrier housing of the axle assembly. Conventionally, a sump in the carrier housing contains lubricant to reduce friction between surfaces including, but not limited to, the pinion gear and ring gear, and a pair of side gears and a pair of pinion carrier gears. The lubricant may also disperse heat generated between the components of the axle assembly.
In conventional axle assemblies, lubricant churning can decrease axle assembly and vehicle efficiency, increase operating temperatures, and reduce the life of axle assembly components. For example, the volume of lubricant in the sump necessary for certain conditions may be excessive in many instances. During ordinary operation of a vehicle including the axle assembly, when torque loads are below a certain value, the volume of lubricant may result in excess windage of the drive pinion, the differential apparatus, and the pair of axles. Parasitic drag may also be exaggerated when the ambient temperature of the carrier housing is greatly reduced, such as during operation in cold weather. Additionally, during operation in cold weather, the volume of lubricant may disperse heat generated between the moving parts at a rate which prevents a viscosity of the volume of lubricant from decreasing, resulting in increased drag.
Reducing the volume of lubricant disposed in the sump to reduce windage also reduces the effectiveness and reliability of the axle assembly in certain conditions. For example, during a torque intensive operation, a reduced volume of lubricant may not adequately reduce the friction generated between contacting parts such as the drive pinion, the differential apparatus, and the pair of axles. As a result, the components may suffer excessive wear and operate in a noisy or harsh manner. Additionally, reduced volume of lubricant may be unable to disperse heat generated between the moving parts at a rate which prevents premature degradation of the lubricant, or causes damage to seals in the carrier housing.
The present subject matter discloses a method and apparatus which enables control of the lubricant level in an axle assembly in a simple and cost effective manner.